Dept. of Physical Chemistry and Chemical Engineering I, University of A Coruña, Rúa da Fraga n°1, 15008 A Coruña, Galiza, Spain.
Chemosphere. 2013 Oct;93(7):1317-23. doi: 10.1016/j.chemosphere.2013.07.043. Epub 2013 Aug 12.
The objective of the present study was to investigate for the first time the long-term removal of heavy metals (HMs) in a combined UASB-CW system treating municipal wastewater. The research was carried out in a field pilot plant constituted for an up-flow anaerobic sludge bed (UASB) digester as a pretreatment, followed by a surface flow constructed wetland (CW) and finally by a subsurface flow CW. While the UASB showed (pseudo) steady state operational conditions and generated a periodical purge of sludge, CWs were characterised by the progressive accumulation and mineralisation of retained solids. This paper analyses the evolution of HM removal from the water stream over time (over a period of 4.7 year of operation) and the accumulation of HMs in UASB sludge and CW sediments at two horizons of 2.7 and 4.0 year of operation. High removal efficiencies were found for some metals in the following order: Sn > Cr > Cu > Pb > Zn > Fe (63-94%). Medium removal efficiencies were registered for Ni (49%), Hg (42%), and Ag (40%), and finally Mn and As showed negative percentage removals. Removal efficiencies of total HMs were higher in UASB and SF units and lower in the last SSF unit.
本研究的目的是首次调查在联合 UASB-CW 系统中处理城市污水时重金属（HMs）的长期去除情况。该研究在一个现场中进行，由上流式厌氧污泥床（UASB）消化器作为预处理，随后是表面流人工湿地（CW），最后是地下流人工湿地。UASB 表现出（拟）稳态操作条件，并定期排出污泥，而 CW 则以保留固体的逐渐积累和矿化为特征。本文分析了随着时间的推移（在 4.7 年的运行期间）从水流中去除 HM 的演变情况，以及在运行 2.7 年和 4.0 年两个时间点时在 UASB 污泥和 CW 沉积物中 HM 的积累情况。对于某些金属，发现了很高的去除效率，顺序如下：Sn > Cr > Cu > Pb > Zn > Fe（63-94%）。对于 Ni（49%）、Hg（42%）和 Ag（40%），登记了中等去除效率，而 Mn 和 As 则显示出负百分比去除。总 HM 的去除效率在 UASB 和 SF 单元中较高，在最后一个 SSF 单元中较低。
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